High molecular weight light-emitting materials that are soluble in solvents are studied since they are capable of forming organic layers in light-emitting devices according to coating methods. As such light-emitting materials, random copolymers of polyfluorenes are known (Patent Literature 1).
Furthermore, as such a light-emitting material, a composition prepared by doping a phosphorescent light-emitting compound, which emits light from a triplet excitation state as a dopant on a host material, is known. It is important for a host material used in preparing such a composition to have a high lowest triplet excitation energy (hereinafter referred to as “T1 energy”).
As an example of the host material having a high T1 energy in relation to a phosphorescent light-emitting compound which emits light having a shorter wavelength than that of red light, a meta-phenylene based polymer compound which comprises a combination of specific constitutional units has been proposed (Patent Literature 2).